iio: magnetometer: rm3100: Modernize locking and refactor control flow

Replace mutex_lock() and mutex_unlock() calls in rm3100-core.c with
the more modern guard(mutex)() family. This will help modernize the
driver and bring it up-to-date with modern available macros/functions.

While replacing mutex_lock() and mutex_unlock(), the critical sections
of rm3100_read_mag() and rm3100_get_samp_freq() have been extended to
include negligible operations for cleaner logic.

Add new helper-wrapper function rm3100_regmap_bulk_read_locked() to
help keep rm3100_trigger_handler() switch-cases clean while maintaining
mutex locking and avoiding re-entrancy risks from potential callbacks.

While at it, remove redundant gotos where applicable, and use direct
returns instead. In addition, remove regmap variable in
rm3100_trigger_handler() as its references have been replaced with
variable data.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Maxwell Doose <m32285159@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/magnetometer/rm3100-core.c b/drivers/iio/magnetometer/rm3100-core.c
index 2b28844257460f385d260dc26b1312b37ac53741..ac3f9f7fc8089c2804b120029a628004dcbcb59e 100644 (file)
--- a/drivers/iio/magnetometer/rm3100-core.c
+++ b/drivers/iio/magnetometer/rm3100-core.c
@@ -204,27 +204,23 @@ static int rm3100_read_mag(struct rm3100_data *data, int idx, int *val)
        u8 buffer[3];
        int ret;
 
-       mutex_lock(&data->lock);
+       guard(mutex)(&data->lock);
+
        ret = regmap_write(regmap, RM3100_REG_POLL, BIT(4 + idx));
        if (ret < 0)
-               goto unlock_return;
+               return ret;
 
        ret = rm3100_wait_measurement(data);
        if (ret < 0)
-               goto unlock_return;
+               return ret;
 
        ret = regmap_bulk_read(regmap, RM3100_REG_MX2 + 3 * idx, buffer, 3);
        if (ret < 0)
-               goto unlock_return;
-       mutex_unlock(&data->lock);
+               return ret;
 
        *val = sign_extend32(get_unaligned_be24(&buffer[0]), 23);
 
        return IIO_VAL_INT;
-
-unlock_return:
-       mutex_unlock(&data->lock);
-       return ret;
 }
 
 #define RM3100_CHANNEL(axis, idx)                                      \
@@ -284,11 +280,12 @@ static int rm3100_get_samp_freq(struct rm3100_data *data, int *val, int *val2)
        unsigned int tmp;
        int ret;
 
-       mutex_lock(&data->lock);
+       guard(mutex)(&data->lock);
+
        ret = regmap_read(data->regmap, RM3100_REG_TMRC, &tmp);
-       mutex_unlock(&data->lock);
        if (ret < 0)
                return ret;
+
        *val = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][0];
        *val2 = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][1];
 
@@ -338,56 +335,50 @@ static int rm3100_set_samp_freq(struct iio_dev *indio_dev, int val, int val2)
        int ret;
        int i;
 
-       mutex_lock(&data->lock);
+       guard(mutex)(&data->lock);
+
        /* All cycle count registers use the same value. */
        ret = regmap_read(regmap, RM3100_REG_CC_X, &cycle_count);
        if (ret < 0)
-               goto unlock_return;
+               return ret;
 
        for (i = 0; i < RM3100_SAMP_NUM; i++) {
                if (val == rm3100_samp_rates[i][0] &&
                    val2 == rm3100_samp_rates[i][1])
                        break;
        }
-       if (i == RM3100_SAMP_NUM) {
-               ret = -EINVAL;
-               goto unlock_return;
-       }
+       if (i == RM3100_SAMP_NUM)
+               return -EINVAL;
 
        ret = regmap_write(regmap, RM3100_REG_TMRC, i + RM3100_TMRC_OFFSET);
        if (ret < 0)
-               goto unlock_return;
+               return ret;
 
        /* Checking if cycle count registers need changing. */
        if (val == 600 && cycle_count == 200) {
                ret = rm3100_set_cycle_count(data, 100);
                if (ret < 0)
-                       goto unlock_return;
+                       return ret;
        } else if (val != 600 && cycle_count == 100) {
                ret = rm3100_set_cycle_count(data, 200);
                if (ret < 0)
-                       goto unlock_return;
+                       return ret;
        }
 
        if (iio_buffer_enabled(indio_dev)) {
                /* Writing TMRC registers requires CMM reset. */
                ret = regmap_write(regmap, RM3100_REG_CMM, 0);
                if (ret < 0)
-                       goto unlock_return;
+                       return ret;
                ret = regmap_write(data->regmap, RM3100_REG_CMM,
                        (*indio_dev->active_scan_mask & 0x7) <<
                        RM3100_CMM_AXIS_SHIFT | RM3100_CMM_START);
                if (ret < 0)
-                       goto unlock_return;
+                       return ret;
        }
-       mutex_unlock(&data->lock);
 
        data->conversion_time = rm3100_samp_rates[i][2] * 2;
        return 0;
-
-unlock_return:
-       mutex_unlock(&data->lock);
-       return ret;
 }
 
 static int rm3100_read_raw(struct iio_dev *indio_dev,
@@ -458,6 +449,27 @@ static const struct iio_buffer_setup_ops rm3100_buffer_ops = {
        .postdisable = rm3100_buffer_postdisable,
 };
 
+/**
+ * rm3100_regmap_bulk_read_locked() - Wrapper around regmap_bulk_read() with a mutex
+ *
+ * @data: Data structure containing regmap and mutex
+ * @reg: First register to be read from, passed to regmap_bulk_read()
+ * @val: Pointer to store read value, in native register size for device,
+ * passed to regmap_bulk_read()
+ * @val_count: Number of registers to read, passed to regmap_bulk_read()
+ *
+ * Intended for use only in rm3100_trigger_handler().
+ *
+ * Return:
+ * A value of zero on success, a negative errno in error cases.
+ */
+static int rm3100_regmap_bulk_read_locked(struct rm3100_data *data, unsigned int reg,
+                                         void *val, size_t val_count)
+{
+       guard(mutex)(&data->lock);
+       return regmap_bulk_read(data->regmap, reg, val, val_count);
+}
+
 static irqreturn_t rm3100_trigger_handler(int irq, void *p)
 {
        struct iio_poll_func *pf = p;
@@ -465,14 +477,12 @@ static irqreturn_t rm3100_trigger_handler(int irq, void *p)
        unsigned long scan_mask = *indio_dev->active_scan_mask;
        unsigned int mask_len = iio_get_masklength(indio_dev);
        struct rm3100_data *data = iio_priv(indio_dev);
-       struct regmap *regmap = data->regmap;
        int ret, i, bit;
 
-       mutex_lock(&data->lock);
        switch (scan_mask) {
        case BIT(0) | BIT(1) | BIT(2):
-               ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 9);
-               mutex_unlock(&data->lock);
+               ret = rm3100_regmap_bulk_read_locked(data, RM3100_REG_MX2,
+                                                    data->buffer, 9);
                if (ret < 0)
                        goto done;
                /* Convert XXXYYYZZZxxx to XXXxYYYxZZZx. x for paddings. */
@@ -480,36 +490,34 @@ static irqreturn_t rm3100_trigger_handler(int irq, void *p)
                        memmove(data->buffer + i * 4, data->buffer + i * 3, 3);
                break;
        case BIT(0) | BIT(1):
-               ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 6);
-               mutex_unlock(&data->lock);
+               ret = rm3100_regmap_bulk_read_locked(data, RM3100_REG_MX2,
+                                                    data->buffer, 6);
                if (ret < 0)
                        goto done;
                memmove(data->buffer + 4, data->buffer + 3, 3);
                break;
        case BIT(1) | BIT(2):
-               ret = regmap_bulk_read(regmap, RM3100_REG_MY2, data->buffer, 6);
-               mutex_unlock(&data->lock);
+               ret = rm3100_regmap_bulk_read_locked(data, RM3100_REG_MY2,
+                                                    data->buffer, 6);
                if (ret < 0)
                        goto done;
                memmove(data->buffer + 4, data->buffer + 3, 3);
                break;
        case BIT(0) | BIT(2):
-               ret = regmap_bulk_read(regmap, RM3100_REG_MX2, data->buffer, 9);
-               mutex_unlock(&data->lock);
+               ret = rm3100_regmap_bulk_read_locked(data, RM3100_REG_MX2,
+                                                    data->buffer, 9);
                if (ret < 0)
                        goto done;
                memmove(data->buffer + 4, data->buffer + 6, 3);
                break;
        default:
                for_each_set_bit(bit, &scan_mask, mask_len) {
-                       ret = regmap_bulk_read(regmap, RM3100_REG_MX2 + 3 * bit,
-                                              data->buffer, 3);
-                       if (ret < 0) {
-                               mutex_unlock(&data->lock);
+                       ret = rm3100_regmap_bulk_read_locked(data,
+                                                            RM3100_REG_MX2 + 3 * bit,
+                                                            data->buffer, 3);
+                       if (ret < 0)
                                goto done;
-                       }
                }
-               mutex_unlock(&data->lock);
        }
        /*
         * Always using the same buffer so that we wouldn't need to set the